/**
 * 
 */
var oDiv = document.getElementById("tab");
var oLi = oDiv.getElementsByTagName("div")[0].getElementsByTagName("li");
var aCon = oDiv.getElementsByTagName("div")[1].getElementsByTagName("div");
var timer = null;
for (var i = 0; i < oLi.length; i++) {
    oLi[i].index = i;
    oLi[i].onclick = function() {
        show(this.index);
    }
}
function show(a) {
    index = a;
    var alpha = 0;
    for (var j = 0; j < oLi.length; j++) {
        oLi[j].className = "";
        aCon[j].className = "";
        aCon[j].style.opacity = 0;
        aCon[j].style.filter = "alpha(opacity=0)";
    }
    oLi[index].className = "cur";
    clearInterval(timer);
    timer = setInterval(function() {
        alpha += 2;
        alpha > 100 && (alpha = 100);
        aCon[index].style.opacity = alpha / 100;
        aCon[index].style.filter = "alpha(opacity=" + alpha + ")";
        alpha == 100 && clearInterval(timer);
    },
    5)
}